Home networking systems commonly use phone lines, power lines or coaxial cables as a communication medium. In some cases, there could be variation in signal attenuation and noise characteristics between various pairs of nodes (also called stations, or devices). In such cases, home networking systems may use channel adaptation procedures that enable selection of unique physical layer encoding and/or modulation parameters (e.g., modulation rate and forward error correction code rate) between a given pair of nodes. This approach enables optimization of the physical data rate that can be achieved between the pair of nodes according to current channel characteristics.
One of the attributes of home networking systems is the Physical Layer Protocol Data Unit (PPDU) format. A PPDU is a physical layer signal that is transmitted on the medium. A PPDU may include several parts or fields such as a preamble, a header and a payload.
Some systems transmit the header in a broadcast mode in which the physical layer encoding and/or modulation is done such that even the furthest station in the network is capable of receiving (i.e., successfully demodulating and decoding) the header.